McDonald's announced Wednesday its plan to fully transition to cage-free eggs in the U.S. and Canada over the next 10 years, joining an increasing number of restaurants and food companies making similar changes to meet consumer demand.

The fast-food giant's decision, lauded by animal welfare groups, could have a major impact on egg suppliers throughout the country. Other companies like Burger King and Aramark have also made cage-free egg commitments in recent years, but the size of McDonald's egg demands for its 16,000-plus restaurants in the U.S. and Canada makes it unique, according to animal welfare experts.

McDonald's USA buys about 2 billion eggs annually — about 2 percent of the country's entire egg supply — a number that factors in increased projections for all-day breakfast set to begin Oct. 6, said Marion Gross, senior vice president of supply chain management for McDonald's USA.

In the U.S., about 13 million of McDonald's eggs annually already come from a cage-free environment, Gross said, but going exclusively cage-free is "a big undertaking."

"We think this is a really significant step we're making," Gross said. "It's just the next step in becoming a modern, progressive burger company."

That phrase "modern, progressive burger company" echoes the words of CEO Steve Easterbrook, who took the reins of McDonald's in March after a prolonged sales decline.

But the shift toward cage-free eggs was set in motion before Easterbrook's hiring, Gross said.

In 2003, the company set standards for the size of hen houses, requiring 5 more inches of space per bird than the industry standard, Gross said. And in 2010, McDonald's began working with the Coalition for Sustainable Egg Supply on a study of the impact of various hen housing systems on animal health, affordability and other factors. The findings, released in March, influenced McDonald's decision, Gross said.

McDonald's will begin rolling out all-day breakfast nationwide on Oct. 6, a long-awaited move that could help boost sales for the flagging burger chain.

The move, following a vote Tuesday by franchisee leadership, is the boldest one yet under McDonald's CEO Steve Easterbrook, who was hired in March...

Gross called the 10-year timeline "really aggressive" for such a shift.

Stephen Herbruck, president of Herbruck's Poultry Ranch, agreed. His Michigan-based company is one of McDonald's largest egg suppliers in the country. About 3 million of its 7 million hens are in cages at a site near Saranac, Mich., dedicated to McDonald's.

In the years to come, that site's 31 buildings will be renovated to meet the new cage-free criteria, two or three buildings per year, Herbruck said.

It could cost his company up to $100 million, he said.

"It's a huge investment," Herbruck said.

He said he applauded McDonald's decision and that his farms had already been moving toward cage-free systems, which allow the birds room to run, nest and feed. "It's more of a natural environment for them," he said.

Most of McDonald's eggs currently come from "conventional" housing, meaning cages that allow 72 square inches per bird, Gross said. Some also come from enriched colony systems, which are larger holding areas with perches and nesting areas.

McDonald's intends to work with its egg suppliers and farms to transition them to a cage-free environment, which still requires a housing structure, she said. For some farms, that will mean increased costs to build the new structures, as well as new watering and waste-removal systems.

As for who's going to pay for the increased costs, Gross said the farms and suppliers would be responsible for new investments needed and their costs would be mitigated by the greater demand from McDonald's and other companies moving in the same direction.

"We don't anticipate our customers will pay more because of this change," Gross said.

Animal welfare groups that have long called for McDonald's to require more humane practices of its suppliers applauded the chain's announcement.

"It makes it more clear than ever before that cages don't have a place in the industry," said Paul Shapiro, president of farm animal protection for the Humane Society of the United States.

Shapiro said McDonald's decision will have more impact than other companies' similar commitments because of its purchasing power. "When (McDonald's) speaks, the egg industry must listen," he said.

Other groups agreed.

"We wholeheartedly commend McDonald's for their announcement to go cage-free with their eggs. We have no doubt their announcement will create a ripple effect in the entire market. This signals the end of the cage age for laying hens in the U.S.," Leah Garces, U.S. director of Compassion in World Farming, said in a statement.

Randy Olson, executive director of the Iowa Egg Council, said he expected there will continue to be demand for both caged and cage-free hens, among other housing options. Decades ago, farms moved to the caged model because of increased demand for low-cost eggs, he said. Now consumer demand seems to be swinging back to the cage-free model.

Some farmers were already moving toward cage-free, Olson said, while others have no intention of changing, regardless of McDonald's decision.

"Moves like this, they catch headlines, but they are not necessarily surprising to the farmers themselves," Olson said.

In 2012, McDonald's set a 10-year timeline for phasing out gestation crates for pregnant sows.